md: add a new parameter 'offset' to md_super_write()

JIRA: https://issues.redhat.com/browse/RHEL-123668

commit d01acbc
Author: Yu Kuai <yukuai3@huawei.com>
Date:   Fri Aug 29 16:04:16 2025 +0800

    md: add a new parameter 'offset' to md_super_write()

    The parameter is always set to 0 for now, following patches will use
    this helper to write llbitmap to underlying disks, allow writing
    dirty sectors instead of the whole page.

    Also rename md_super_write to md_write_metadata since there is nothing
    super-block specific.

    Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-2-yukuai1@huaweicloud.com
    Signed-off-by: Yu Kuai <yukuai3@huawei.com>
    Reviewed-by: Xiao Ni <xni@redhat.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Hannes Reinecke <hare@suse.de>
    Reviewed-by: Li Nan <linan122@huawei.com>

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>

Author: ncroxon

drivers/md/md-bitmap.c

@@ -483,7 +483,8 @@ static int __write_sb_page(struct md_rdev *rdev, struct bitmap *bitmap,
 			return -EINVAL;
 	}
 
-	md_super_write(mddev, rdev, sboff + ps, (int)min(size, bitmap_limit), page);
+	md_write_metadata(mddev, rdev, sboff + ps, (int)min(size, bitmap_limit),
+			  page, 0);
 	return 0;
 }
 

drivers/md/md.c

@@ -1016,15 +1016,26 @@ static void super_written(struct bio *bio)
 		wake_up(&mddev->sb_wait);
 }
 
-void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
-		   sector_t sector, int size, struct page *page)
-{
-	/* write first size bytes of page to sector of rdev
-	 * Increment mddev->pending_writes before returning
-	 * and decrement it on completion, waking up sb_wait
-	 * if zero is reached.
-	 * If an error occurred, call md_error
-	 */
+/**
+ * md_write_metadata - write metadata to underlying disk, including
+ * array superblock, badblocks, bitmap superblock and bitmap bits.
+ * @mddev:	the array to write
+ * @rdev:	the underlying disk to write
+ * @sector:	the offset to @rdev
+ * @size:	the length of the metadata
+ * @page:	the metadata
+ * @offset:	the offset to @page
+ *
+ * Write @size bytes of @page start from @offset, to @sector of @rdev, Increment
+ * mddev->pending_writes before returning, and decrement it on completion,
+ * waking up sb_wait. Caller must call md_super_wait() after issuing io to all
+ * rdev. If an error occurred, md_error() will be called, and the @rdev will be
+ * kicked out from @mddev.
+ */
+void md_write_metadata(struct mddev *mddev, struct md_rdev *rdev,
+		       sector_t sector, int size, struct page *page,
+		       unsigned int offset)
+{
 	struct bio *bio;
 
 	if (!page)
@@ -1042,7 +1053,7 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
 	atomic_inc(&rdev->nr_pending);
 
 	bio->bi_iter.bi_sector = sector;
-	__bio_add_page(bio, page, size, 0);
+	__bio_add_page(bio, page, size, offset);
 	bio->bi_private = rdev;
 	bio->bi_end_io = super_written;
 
@@ -1652,8 +1663,8 @@ super_90_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
 	if ((u64)num_sectors >= (2ULL << 32) && rdev->mddev->level >= 1)
 		num_sectors = (sector_t)(2ULL << 32) - 2;
 	do {
-		md_super_write(rdev->mddev, rdev, rdev->sb_start, rdev->sb_size,
-		       rdev->sb_page);
+		md_write_metadata(rdev->mddev, rdev, rdev->sb_start,
+				  rdev->sb_size, rdev->sb_page, 0);
 	} while (md_super_wait(rdev->mddev) < 0);
 	return num_sectors;
 }
@@ -2301,8 +2312,8 @@ super_1_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
 	sb->super_offset = cpu_to_le64(rdev->sb_start);
 	sb->sb_csum = calc_sb_1_csum(sb);
 	do {
-		md_super_write(rdev->mddev, rdev, rdev->sb_start, rdev->sb_size,
-			       rdev->sb_page);
+		md_write_metadata(rdev->mddev, rdev, rdev->sb_start,
+				  rdev->sb_size, rdev->sb_page, 0);
 	} while (md_super_wait(rdev->mddev) < 0);
 	return num_sectors;
 
@@ -2811,18 +2822,17 @@ void md_update_sb(struct mddev *mddev, int force_change)
 			continue; /* no noise on spare devices */
 
 		if (!test_bit(Faulty, &rdev->flags)) {
-			md_super_write(mddev,rdev,
-				       rdev->sb_start, rdev->sb_size,
-				       rdev->sb_page);
+			md_write_metadata(mddev, rdev, rdev->sb_start,
+					  rdev->sb_size, rdev->sb_page, 0);
 			pr_debug("md: (write) %pg's sb offset: %llu\n",
 				 rdev->bdev,
 				 (unsigned long long)rdev->sb_start);
 			rdev->sb_events = mddev->events;
 			if (rdev->badblocks.size) {
-				md_super_write(mddev, rdev,
-					       rdev->badblocks.sector,
-					       rdev->badblocks.size << 9,
-					       rdev->bb_page);
+				md_write_metadata(mddev, rdev,
+						  rdev->badblocks.sector,
+						  rdev->badblocks.size << 9,
+						  rdev->bb_page, 0);
 				rdev->badblocks.size = 0;
 			}
 

drivers/md/md.h

@@ -908,8 +908,9 @@ void md_account_bio(struct mddev *mddev, struct bio **bio);
 void md_free_cloned_bio(struct bio *bio);
 
 extern bool __must_check md_flush_request(struct mddev *mddev, struct bio *bio);
-extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
-			   sector_t sector, int size, struct page *page);
+void md_write_metadata(struct mddev *mddev, struct md_rdev *rdev,
+		       sector_t sector, int size, struct page *page,
+		       unsigned int offset);
 extern int md_super_wait(struct mddev *mddev);
 extern int sync_page_io(struct md_rdev *rdev, sector_t sector, int size,
 		struct page *page, blk_opf_t opf, bool metadata_op);